Magnetic random access memory

ABSTRACT

MTJ elements are accumulated in a plurality of portions on a semiconductor substrate. A first conductive line functioning as a read line and extending in the X direction is connected to pin layers of the MTJ elements. A second conductive line functioning as a write line and read line and extending in the X direction is connected to free layers of the MTJ elements. A write line extends in the Y direction and is shared with two MTJ elements present above and below the write line. The two MTJ elements present above and below the write line are arranged symmetric to the write line.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Applications No. 2001-367754, filed Nov. 30,2001; No. 2001-367755, filed Nov. 30, 2001; and No. 2001-367941, filedNov. 30, 2001, the entire contents of all of which are incorporatedherein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a magnetic random access memory (MRAM)in which a memory cell is constructed using MTJ (Magnetic TunnelJunction) elements having “1”, “0”-information stored therein by atunneling magneto resistive effect.

2. Description of the Related Art

In recent years, there have been proposed many memories havinginformation stored therein by new principle, and one of them is a memoryusing a tunneling magneto resistive (hereinafter, denoted as TMR) effectproposed by Roy Scheuerlein et. al (for example, refer to ISSCC2000Technical Digest p. 128 “A 10 ns Read and Write Non-Volatile MemoryArray Using a Magnetic Tunnel Junction and FET Switch in each cell”).

The magnetic random access memory stores “1”, “0”-information by the MTJelements. The MTJ elements have a structure in which an insulation layer(tunnel barrier) is sandwiched with two ferromagnetic layers. Theinformation stored in the MTJ elements is determined by whether or notthe orientations of spins of the two ferromagnetic layers are parallelor anti-parallel.

Here, parallel means that the orientations of the spins of the twoferromagnetic layers are same, and anti-parallel means that theorientations of the spins of the two ferromagnetic layers are oppositeto each other.

Generally, one of the two ferromagnetic layers constructing the MTJelement is a pin layer in which the orientation of the spin is pinned.When “1”, “0”-information is stored in the MTJ elements, the orientationof the other one (free layer) of the two ferromagnetic layers is variedaccording to written information.

BRIEF SUMMARY OF THE INVENTION

A magnetic random access memory according to a first aspect of thepresent invention comprises: first and second MTJ elements eachconfigured with a first magnetic layer in which the orientation of aspin is pinned, a second magnetic layer in which data is stored, and aninsulation layer sandwiched between the first and second magneticlayers; and a first write line which is arranged between the first andsecond MTJ elements and generates magnetic fields acting on the firstand second MTJ elements. A positional relationship between the firstmagnetic layer, the insulation layer, and the second magnetic layerconstructing the first MTJ element and the first magnetic layer, theinsulation layer, and the second magnetic layer constructing the secondMTJ element is symmetric to the first write line.

A magnetic random access memory according to a second aspect of thepresent invention comprises: an array having a plurality of MTJ elementsaccumulated in a plurality of portions; a first conductive line arrangedin the array; and a second conductive line arranged in the array whichhas the same function as the first conductive line and is arranged abovethe first conductive line, wherein the first and second conductive linesare connected in serial.

A magnetic random access memory according to a third aspect of thepresent invention comprises: an array having a plurality of MTJ elementsaccumulated in a plurality of portions; and a first write line whichextends in the direction in which the plurality of MTJ elements areaccumulated and is provided for generating a magnetic field duringwriting.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

FIG. 1 is a section view showing a reference example of the inventionrelating to a wiring sharing;

FIG. 2 is a section view showing the reference example of the inventionrelating to the wiring sharing;

FIG. 3 is a section view showing a first embodiment of the inventionrelating to the wiring sharing;

FIG. 4 is a section view showing a second embodiment of the inventionrelating to the wiring sharing;

FIG. 5 is a section view showing a third embodiment of the inventionrelating to the wiring sharing;

FIG. 6 is a plan view showing a reference example of the inventionrelating to a serial/parallel connection wiring;

FIG. 7 is a plan view showing a first embodiment of the inventionrelating to the serial/parallel connection wiring;

FIG. 8 is a section view along the X direction of a structure of FIG. 7;

FIG. 9 is a section view along the Y direction of the structure of FIG.7;

FIG. 10 is a section view showing a second embodiment of the inventionrelating to the serial/parallel connection wiring;

FIG. 11 is a section view along the Y direction of a structure of FIG.10;

FIG. 12 is a section view showing a third embodiment of the inventionrelating to the serial/parallel connection wiring;

FIG. 13 is a section view showing a fourth embodiment of the inventionrelating to the serial/parallel connection wiring;

FIG. 14 is a section view showing a fifth embodiment of the inventionrelating to the serial/parallel connection wiring;

FIG. 15 is a section view along the Y direction of a structure of FIG.14;

FIG. 16 is a section view showing a sixth embodiment of the inventionrelating to the serial/parallel connection wiring;

FIG. 17 is a perspective view showing a reference example of theinvention relating to a three-dimensional wiring;

FIG. 18 is a section view showing the reference example of the inventionrelating to the three-dimensional wiring;

FIG. 19 is a perspective view showing the reference example of theinvention relating to the three-dimensional wiring;

FIG. 20 is a section view showing the reference example of the inventionrelating to the three-dimensional wiring;

FIG. 21 is a perspective view showing a first embodiment of theinvention relating to the three-dimensional wiring;

FIG. 22 is a perspective view showing a second embodiment of theinvention relating to the three-dimensional wiring;

FIG. 23 is a perspective view showing a third embodiment of theinvention relating to the three-dimensional wiring;

FIG. 24 is a perspective view showing a fourth embodiment of theinvention relating to the three-dimensional wiring;

FIG. 25 is a perspective view showing a fifth embodiment of theinvention relating to the three-dimensional wiring;

FIG. 26 is a plan view showing a positional relationship between a writeline and MTJ elements;

FIG. 27 is a perspective view showing a sixth embodiment of theinvention relating to the three-dimensional wiring;

FIG. 28 is a perspective view showing a seventh embodiment of theinvention relating to the three-dimensional wiring; and

FIG. 29 is a perspective view showing the seventh embodiment of theinvention relating to the three-dimensional wiring.

DETAILED DESCRIPTION OF THE INVENTION

Hereinafter, a magnetic random access memory according to embodiments ofthe present invention will be described in detail with reference to thedrawings.

(1) Presupposed Technique

In recent years, various MRAMs of device structure or circuit structurehave been proposed, and one of them has a device structure in which aplurality of MTJ elements are connected to one switching element(selective transistor). This structure is advantageous for high densityof cells or improvement of read margins.

For example, in a ladder type cell structure, a plurality of MTJelements are connected in parallel between upper lines and lower lines.In this cell structure, as shown in FIG. 1, a plurality of MTJ elements10 are accumulated in a plurality of portions (in this example, fourportions) on a substrate. Further, in each portion, a plurality of MTJelements 10 are connected in parallel between upper lines 11 and lowerlines 12.

The upper lines 11 extend in the X direction, and one ends thereof areconnected to selective transistors 14. The lower lines 12 also extend inthe X direction, and one ends thereof are connected to peripheralcircuits such as sense amplifiers (S/A) 15. In this example, a readcurrent flows in the path from the upper lines 11 through the MTJelements 10 to the lower lines 12, that is along the X direction. Writelines 13 are arranged adjacent to the MTJ elements 10, and extend in theY direction.

The cell structure of FIG. 2 is an example in which the lower line inFIG. 1 and the write line are integrated. In other words, the lower line12 extends in the Y direction, and one end thereof is connected to thesense amplifier (S/A). During writing, the lower line 12 functions as awrite line. During reading, the lower line 12 functions as a read line.That is, the read current flows through the upper line (X direction) 11at first, and then flows via the MTJ elements 10 to the lower line (Ydirection) 12.

A basic structure of a cell of the magnetic random access memory is a 1cell-1 transistor structure in which one switching element (selectivetransistor) is corresponded to one MTJ element. However, in the devicestructure in which the MTJ elements are accumulated in a plurality ofportions, when one switching element is corresponded to one MTJ element,the number of switching elements becomes larger, which isdisadvantageous for high density of cells.

In the case of the device structure in which the MTJ elements 10 areaccumulated in a plurality of portions, there is employed the devicestructure in which, even when one switching element is not correspondedto one MTJ element, read operation or write operation can be performed.

For example, in the device structure shown in FIGS. 1 and 2, a pluralityof MTJ elements 10 are connected between the upper lines 11 and thelower lines 12 in each portion of an array of the MTJ elements 10.Further, for example, the selective transistors 14 are connected to oneends of the upper lines 11, and the sense amplifiers (S/A) 15 areconnected to one ends of the lower lines 12.

However, in this case, in the example of FIG. 1, three lines of theupper line (read/write line) 11, the lower line (read line) 12, and thewrite line 13 in total have to be arranged in each portion of the arrayof the MTJ elements 10. Further, in the example of FIG. 2, two lines ofthe upper line (read/write line) 11 and the lower line (read/write line)12 in total have to be arranged in each portion of the array of the MTJelements 10.

In the case where such a write line or read line (current path line) isarranged in the array of the MTJ elements accumulated in a plurality ofportions on the substrate, when the number of accumulated portions ofthe MTJ elements becomes larger, there arise the problems that thedevice structure becomes complicated and process cost is increased dueto increase in the number of manufacturing steps.

Further, the characteristics of the MTJ elements are largely influencedby the flatness of the surfaces (base films) on which the MTJ elementsare arranged. Since this flatness is more affected when the number ofaccumulated portions of the MTJ elements becomes larger, there is aproblem that the characteristics of the MTJ elements are deterioratedalong with the increase in the number of accumulated portions of the MTJelements.

(2) Outline

The embodiments according to the present invention (sharing of wiring)are applied to a magnetic random access memory having an array structurein which the MTJ elements are accumulated in a plurality of portions.The magnetic random access memory according to the embodiments of thepresent invention is characterized in that one of two write linesrequired for one MTJ element is shared with two MTJ elements adjacent inthe vertical direction. Further, the two MTJ elements are arrangedsymmetric to each other relative to the shared write line.

Accordingly, the number of conductive lines arranged in the array of theMTJ elements can be decreased so that reduction of process cost can beachieved by reduction of the number of manufacturing steps. In addition,deterioration of the flatness along with the increase in the number ofaccumulated portions of the MTJ elements can also be restricted, therebyimproving the characteristics of the MTJ elements.

(3) Embodiments

{circle around (1)} First Embodiment

FIG. 3 shows a cell array section of a magnetic random access memoryaccording to a first embodiment of the present invention.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, four portions) on the semiconductorsubstrate. The MTJ elements 10 construct the array in the X-Y plane ineach portion. In FIG. 3, the MTJ elements along the Y direction areomitted.

The write line 13 is arranged between two MTJ elements 10 adjacent inthe vertical direction, and extends in the Y direction. In the presentembodiment, since the write line 13 is shared with two MTJ elementsadjacent in the vertical direction, the following cell structure isemployed. In other words, the write lines 13 are not arranged betweenall the portions, but are arranged, for example, immediately above theMTJ elements 10 in the odd portions and immediately below the MTJelements 10 in the even portions from the semiconductor substrate side.

In the present embodiment, the write lines 13 are arranged between theMTJ elements in the first portion and the MTJ elements in the secondportion, and between the MTJ elements in the third portion and the MTJelements in the fourth portion from the semiconductor substrate side,respectively. That is, the write line 13 is not arranged between the MTJelements in the second portion and the MTJ elements in the third portionfrom the semiconductor substrate side.

Further, in the present embodiment, two MTJ elements present above andbelow the write line 13 are arranged symmetric to each other relative tothe write line 13.

More specifically, the MTJ element 10 is configured with two magneticlayers (ferromagnetic layers) and an insulation layer (tunnel barrier)sandwiched therewith, where a pin layer in which the orientation of aspin is pinned of the two magnetic layers is arranged far away from thewrite line 13. Further, a free layer in which the orientation of thespin can be freely changed of the two magnetic layers is arranged nearthe write line 13. The write line 13 is positioned equidistantly fromthe two MTJ elements 10 present above and below the write line 13, andis separated from the two MTJ elements 10.

In each portion, a first conductive line 11A functioning as a read lineis connected to the pin layer of the MTJ element 10. The firstconductive line 11A extends in the X direction, and is commonlyconnected to the pin layers of a plurality of MTJ elements 10 arrangedin the X direction. The sense amplifier (S/A) 15 is connected to one endof the first conductive line 11A.

Further, in each portion, a second conductive line 12A functioning as awrite line and read line is connected to the free layer of the MTJelement 10. The second conductive line 12A extends in the X direction,and is commonly connected to the free layers of a plurality of MTJelements 10 arranged in the X direction. The switching element 14functioning as a selective transistor is connected to one end of thesecond conductive line 12A.

According to such a cell structure of the first embodiment, one of twowrite lines required for writing data in one MTJ element is shared withtwo MTJ elements adjacent in the vertical direction. In this way, it ispossible to reduce the number of conductive lines arranged in the arrayof the MTJ elements so that the reduction of process cost can beachieved by the reduction of the number of manufacturing steps.Moreover, the deterioration of the flatness along with the increase inthe number of accumulated portions of the MTJ elements can also berestricted, thereby improving the characteristics of the MTJ elements.

Further, according to the cell structure of the first embodiment, twoMTJ elements arranged above and below the write line are arrangedsymmetric to each other relative to the write line. Thereby, withrespect to the magnetic fields generated by the current flowing throughthe write line, the intensities of the magnetic fields acting on thefree layers of the two MTJ elements arranged above and below the writeline are substantially same so that it is possible to restrictvariations of the magnetic fields acting on the respective MTJ elements.

{circle around (2)} Second Embodiment

FIG. 4 shows a cell array section of a magnetic random access memoryaccording to a second embodiment of the present invention.

The magnetic random access memory according to the present embodiment ischaracterized in that the read lines 12A of FIG. 3 are omitted and thewrite lines 13 of FIG. 3 each have a function as a read line as comparedwith the magnetic random access memory of FIG. 3.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, four portions) on the semiconductorsubstrate. Further, the MTJ elements 10 construct the array in the X-Yplane in each portion. In FIG. 4, the MTJ elements along the Y directionare omitted.

In each portion, the first conductive line 11A functioning as a writeline and read line is connected to the free layer of the MTJ element 10.The first conductive line 11A extends in the X direction, and iscommonly connected to the free layers of a plurality of MTJ elements 10arranged in the X direction. The switching element 14 as a selectivetransistor is connected to one end of the first conductive line 11A.

Further, in each portion, the second conductive line 12A functioning asa write line and read line is connected to the pin layer of the MTJelement 10. The second conductive line 12A extends in the Y direction,and is commonly connected to the pin layers of a plurality of MTJelements 10 arranged in the Y direction. The sense amplifier (S/A) isconnected to one end of the second conductive line 12A.

The second conductive line 12A is arranged between two MTJ elements 10adjacent in the vertical direction. In other words, the secondconductive line 12A is shared with two MTJ elements adjacent in thevertical direction. Therefore, the second conductive lines 12A are notarranged between all the portions, but are arranged, for example,immediately above the MTJ elements 10 in the odd portions, andimmediately below the MTJ elements 10 in the even portions from thesemiconductor substrate side.

In the present embodiment, the second conductive lines 12A are arrangedbetween the MTJ elements in the first portion and the MTJ elements inthe second portion, and between the MTJ elements in the third portionand the MTJ elements in the fourth portion from the semiconductorsubstrate side, respectively. That is, the second conductive line 12A isnot arranged between the MTJ elements in the second portion and the MTJelements in the third portion from the semi-conductor substrate side.

Further, in the present embodiment, two MTJ elements present above andbelow the second conductive line 12A are arranged symmetric to eachother relative to the second conductive line 12A. In other words, theMTJ element 10 is configured with two magnetic layers (ferromagneticlayers) and an insulation layer (tunnel barrier) sandwiched therewith,where the pin layer in which the orientation of the spin is pinned ofthe two magnetic layers is near the second conductive line 12A. Further,the free layer in which the orientation of the spin can be freelychanged of the two magnetic layers is arranged far away from the secondconductive line 12A.

According to such a cell structure of the second embodiment, one of twowrite lines required for writing data in one MTJ element is shared withtwo MTJ elements adjacent in the vertical direction. Since a write-onlyconductive line or a read-only conductive line is eliminated and oneconductive line is used for both writing and reading, the number ofconductive lines can be remarkably reduced. In the present embodiment,the number of conductive lines for one MTJ element is substantially 1.5.This enables to achieve the reduction of process cost by the reductionof the number of manufacturing steps. Moreover, it is possible torestrict the deterioration of the flatness along with the increase inthe number of accumulated portions of the MTJ elements, therebyimproving the characteristics of the MTJ elements.

In addition, according to the cell structure of the second embodiment,two MTJ elements arranged above and below the write line are arranged tobe symmetric to each other relative to the write line. In this way, withrespect to the magnetic fields generated by the current flowing throughthe write line, the intensities of the magnetic fields acting on thefree layers of the two MTJ elements arranged above and below the writeline are substantially same so that it is possible to restrict thevariations of the magnetic fields acting on the respective MTJ elements.

{circle around (3)} Third Embodiment

FIG. 5 shows a cell array section of a magnetic random access memoryaccording to a third embodiment of the present invention.

The magnetic random access memory according to the present embodiment ischaracterized in that the first conductive line (write line and readline) 11A of FIG. 4 is shared with two MTJ elements adjacent in thevertical direction as compared with the magnetic random access memory ofFIG. 4.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, eight portions) on thesemiconductor substrate. Further, the MTJ elements 10 construct thearray in the X-Y plane in each portion. In FIG. 5, the MTJ elementsalong the Y direction are omitted.

In each portion, the first conductive line 11A functioning as a writeline and read line is connected to the free layer of the MTJ element 10.The first conductive line 11A extends in the X direction, and iscommonly connected to the free layers of a plurality of MTJ elements 10arranged in the X direction. The switching element 14 as a selectivetransistor is connected to one end of the first conductive line 11A.

The first conductive line 11A is arranged between two MTJ elements 10adjacent in the vertical direction. More specifically, the firstconductive line 11A is shared with two MTJ elements adjacent in thevertical direction. Therefore, the first conductive lines 11A are notarranged between all the portions, but are arranged, for example,immediately below the MTJ elements 10 in the odd portions, andimmediately above the MTJ elements 10 in the even portions from thesemiconductor substrate side.

In the present embodiment, the first conductive lines 11A are arrangedimmediately below the MTJ elements in the first portion, between the MTJelements in the second portion and the MTJ elements in the thirdportion, between the MTJ elements in the fourth portion and the MTJelements in the fifth portion, between the MTJ elements in the sixthportion and the MTJ elements in the seventh portion, and immediatelyabove the MTJ elements in the eighth portion from the semiconductorsubstrate, respectively.

Further, in the present embodiment, two MTJ elements present above andbelow the first conductive line 11A are arranged symmetric to each otherrelative to the first conductive line 11A. In other words, the MTJelement 10 is configured with two magnetic layers (ferromagnetic layers)and an insulation layer (tunnel barrier) sandwiched therewith, where thepin layer in which the orientation of the spin is pinned of the twomagnetic layers is arranged far away from the first conductive line 11A.The free layer in which the orientation of the spin can be freelychanged of the two magnetic layers is arranged near the first conductiveline 11A.

Moreover, in each portion, the second conductive line 12A functioning asa write line and read line is connected to the pin layer of the MTJelement 10. The second conductive line 12A extends in the Y direction,and is commonly connected to the pin layers of a plurality of MTJelements 10 arranged in the Y direction. The sense amplifier (S/A) isconnected to one end of the second conductive line 12A.

The second conductive line 12A is arranged between two MTJ elements 10adjacent in the vertical direction. That is, the second conductive line12A is shared with two MTJ elements adjacent in the vertical direction.Therefore, the second conductive lines 12A are not arranged between allthe portions, are arranged, for example, immediately above the MTJelements 10 in the odd portions and immediately below the MTJ elements10 in the even portions from the semiconductor substrate side.

In the present embodiment, the second conductive lines 12A are arrangedbetween the MTJ elements in the first portion and the MTJ elements inthe second portion, between the MTJ elements in the third portion andthe MTJ elements in the fourth portion, between the MTJ elements in thefifth portion and the MTJ elements in the sixth portion, and between theMTJ elements in the seventh portion and the MTJ elements in the eighthportion from the semiconductor substrate side, respectively.

Further, in the present embodiment, two MTJ elements present above andbelow the second conductive line 12A are arranged symmetric to eachother relative to the second conductive line 12A. In other words, theMTJ element 10 is configured with two magnetic layers (ferromagneticlayers) and an insulation layer (tunnel barrier) sandwiched therewith,where the pin layer in which the orientation of the spin is pinned ofthe two magnetic layers is arranged near the second conductive line 12A.Moreover, the free layer in which the orientation of the spin can befreely changed of the two magnetic layers is arranged far away from thesecond conductive line 12A.

According to such a cell structure of the third embodiment, theconductive line connected to the free layers of the MTJ elements and theconductive line connected to the pin layers are set to the lines eachcapable of being used as a write line and read line, respectively, andare each shared with two MTJ elements adjacent in the verticaldirection.

Thereby, the number of conductive lines arranged in the array of the MTJelements can be remarkably reduced so that the reduction of process costcan be achieved by the reduction of the number of manufacturing steps.Further, it is also possible to restrict the deterioration of theflatness along with the increase in the number of accumulated portionsof the MTJ elements, thereby improving the characteristics of the MTJelements.

In addition, according to the cell structure of the third embodiment,two MTJ elements arranged above and below the write line are arranged tobe symmetric to each other relative to the write line. In this way, withrespect to the magnetic fields generated by the current flowing throughthe write line, the intensities of the magnetic fields acting on thefree layers of the two MTJ elements arranged above and below the writeline are substantially same so that it is possible to restrict thevariations of the magnetic fields acting on the respective MTJ elements.

(4) Others

In the first to third embodiments described above, description is madeon the premise of a device in which the write line (or read line) iscommonly connected to the MTJ elements in the X direction or Y directionin each portion of the array structure in which a plurality of MTJelements are accumulated in a plurality of portions, but an applicationof the present invention is not limited to such a device.

In the present invention, the magnetic random access memory having anarray structure in which a plurality of MTJ elements are accumulated ina plurality of portions can be applied to any devices having anystructure.

Further, in the first to third embodiments described above, thetransistors connected to the lines in the array of the MTJ elements aregenerally MOS transistors, but may be bipolar transistors, diodes, orthe like.

(5) Conclusion

Hereinbefore, as described above, according to the magnetic randomaccess memory of the embodiments of the present invention, when at leastone of the write lines is shared with MTJ elements present above andbelow the write line, the number of conductive lines arranged in thearray of the MTJ elements can be reduced so that the reduction ofprocess cost can be achieved by the reduction of the number ofmanufacturing steps. In addition, since the number of conductive linesarranged in the array of the MTJ elements is reduced, it is possible torestrict the deterioration of the flatness along with the increase inthe number of accumulated portions of the MTJ elements, therebyimproving the characteristics of the MTJ elements.

2. Serial (Meandering)/Parallel Connection Wiring

(1) Presupposed Technique

A basic structure of the magnetic random access memory is a 1 cell-1transistor structure in which one switching element (selectivetransistor) is corresponded to one MTJ element. However, in the devicestructure in which the MTJ elements are accumulated in a plurality ofportions, when one switching element is corresponded to one MTJ element,the number of switching elements is increased, which is disadvantageousfor high density of the cells.

In the case of the device structure in which the MTJ elements 10 areaccumulated in a plurality of portions, there is employed the devicestructure in which read operation or write operation can be conductedeven when one switching element is not corresponded to one MTJ element.

For example, in the device structure shown in FIGS. 1 and 2, in eachportion of the array of the MTJ elements 10, a plurality of MTJ elements10 are connected between the upper line 11 and the lower line 12. Then,for example, the selective transistor 14 is connected to one end of theupper line 11, and the sense amplifier (S/A) 15 is connected to one endof the lower line 12.

However, in this case, in the example of FIG. 1, the selectivetransistors are required for the respective upper lines 11 arranged ineach portion of the array of the MTJ elements 10. Further, as shown inFIG. 6, the upper lines 11 extend in the X direction on the array 16 ofthe MTJ elements 10. In other words, the selective transistors connectedto the upper lines 11 are intensively arranged in an area 17 at the endof the array 16.

Similarly, the sense amplifiers (transistors) are required for therespective lower lines (read lines) 12 arranged in each portion of thearray of the MTJ elements 10. That is, as shown in FIG. 6, since thelower lines 12 extend in the X direction on the array 16 of the MTJelements 10, the transistors connected to the lower lines 12 areintensively arranged in an area 18 at the end of the array 16.

Similarly, the selective transistors are also required for therespective write lines 13 arranged in each portion of the array of theMTJ elements 10. In other words, as shown in FIG. 6, since the writelines 13 extend in the Y direction on the array 16 of the MTJ elements10, the selective transistors connected to the write lines 13 areintensively arranged in areas 19A and 19B at the end of the array 16.

In data write/read operation with respect to the MTJ elements, it isknown that a large current is required due to the characteristics of theMTJ elements. Therefore, it is expected that the size of the transistorsconnected to the upper lines 11, lower lines 12, and the write lines 13inevitably becomes larger.

Therefore, the area of the areas 17, 18, 19A, and 19B arranged on theperiphery of the array 16 in which the transistors for current drivingare arranged is also increased so that it is impossible to achievereduction of the chip size, reduction of process cost per chip, and thelike. In addition, since the number of selective transistors is alsoincreased in proportion to the number of accumulated portions of the MTJelements, when the number of accumulated portions of the MTJ elements isremarkably increased, a great deal of time is required for the layout ofthe selective transistors, which causes long development time.

(2) Outline

Embodiments of the present invention (serial/parallel connection wiring)are applied to a magnetic random access memory having an array structurein which the MTJ elements are accumulated in a plurality of portions.

The magnetic random access memory according to the embodiments of thepresent invention is characterized in that a plurality of conductivelines (for example, write lines, read lines, or the like) having thesame function which are arranged by one line per portion are connectedin serial or in parallel in one row or column of the array of the MTJelements. In this case, the transistors may be arranged by onetransistor at one ends or both ends of the conductive lines connected inserial/in parallel, respectively so that the number of transistorsarranged at the end of the array of the MTJ elements can be decreased.

Further, according to the device structure of the embodiments of thepresent invention, the transistors may be connected to the conductivelines connected in serial or in parallel in one row or column of thearray of the MTJ elements irrespective of the number of accumulatedportions of the MTJ elements. Accordingly, even when the number ofaccumulated portions of the MTJ elements is increased and increase inthe memory capacity is achieved, the number of transistors is notincreased and the layout thereof does not become complicated.

Moreover, in one row or column of the array of the MTJ elements, sincethe number of transistors is always constant irrespective of the numberof accumulated portions of the MTJ elements, assuming that the array ofthe MTJ elements is one small block, a large memory cell array may beconfigured with a plurality of blocks. In this case, core circuits ofthe transistors or the sense amplifiers may be arranged immediatelybelow the array of the MTJ elements.

(3) Embodiments

{circle around (1)} First Embodiment

FIG. 7 shows a layout of a cell array section of a magnetic randomaccess memory according to a first embodiment of the present invention.FIG. 8 shows a section along the X direction of the cell array sectionof FIG. 7, that is a section along the line VIII-VIII of FIG. 7.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, three portions) on thesemiconductor substrate. Further, the MTJ elements 10 construct thearray in the X-Y plane in each portion.

The upper line 11 and the lower line 12 both extend in the X direction,and a plurality of MTJ elements 10 arranged in the X direction arearranged between both the lines 11 and 12. The selective transistor 14is connected to one end of the upper line 11. Further, the peripheralcircuit such as the sense amplifier (S/A) 15 is connected to one end ofthe lower line 12.

In the present embodiment, the upper line 11 and the lower line 12 eachfunction as a read line. In other words, the read current flows in thepath from the upper line 11 through the MTJ elements 10 to the lowerline 12, that is along the X direction during data reading.

As a specific reading method, at first, the read current is flowedthrough the upper line 11 and the lower line 12, and the potential ofthe lower line 12 at this time is detected by the sense amplifier, forexample. Next, predetermined data (“0” or “1”) is written into theselected MTJ elements (memory cells), and then the read current isflowed through the upper line 11 and the lower line 12 again, and thepotential of the lower line 12 at this time is detected by the senseamplifier. Between the first and second readings, when the potentialsdetected by the sense amplifier are same, data of the selected MTJelements is determined to be same as the predetermined data, and whenthe potentials are different from each other, the data of the selectedMTJ elements is determined to be different from the predetermined data.Finally, correct data is rewritten into the selected MTJ elements.

The write lines 13 are arranged above the MTJ elements 10 and extend inthe Y direction in each portion of the array of the MTJ elements 10.Further, the write lines 13 are arranged in the vicinity of the freelayers of the MTJ elements 10. Moreover, when a group of a plurality ofMTJ elements arranged in the X direction is assumed to be one column anda group of a plurality of MTJ elements arranged in the Y direction isassumed to be one row, the write lines 13 arranged in each portion areconnected in serial in one row of the array of the MTJ elements 10 inthe present embodiment.

More specifically, as shown in FIG. 9, the write line 13 in the upperportion and the write line 13 in the lower portion are electricallyconnected to each other via contact plugs at the end of the array of theMTJ elements 10. In FIG. 9, the upper lines and the lower lines areomitted for simplicity.

As a specific writing method, for example, a write current in onedirection or another direction is flowed according to a value of thewrite data through the lower line 12 functioning as a write line in oneselected column. Simultaneously, the write current in one direction isflowed through the write line 13 in one selected row. In this way, thepredetermined data is written into the MTJ elements (memory cells) 10arranged between the lower line 12 and the write line 13.

As described above, in the present embodiment, the lines having the samefunction arranged in each portion, that is the write lines are connectedin serial in one row of the array of the MTJ elements 10 so that thetransistors may be arranged by one transistor at both ends of the writeline. This allows to remarkably reduce the number of transistorsarranged in the areas 19A and 19B at the end of the array 16 of the MTJelements 10.

Further, according to such a device structure, the transistor may beconnected to the conductive line connected in serial in one row of thearray 16 of the MTJ elements 10 irrespective of the number ofaccumulated portions of the MTJ elements 10. Therefore, even when thenumber of accumulated portions of the MTJ elements 10 is increased sothat the increase in the memory capacity is achieved, the number oftransistors is not increased and the layout thereof does not becomecomplicated.

In addition, since the number of transistors connected to the writelines 13 arranged in each portion in one row of the array 16 of the MTJelements 10 is always constant, assuming that the array 16 of the MTJelements 10 is one small block, a large memory cell array may beconstructed by a plurality of blocks. In this case, for example, asshown in FIG. 9, the core circuits such as the transistors or senseamplifiers may be arranged immediately below the MTJ elements 10 in eachblock.

In FIG. 7, the accumulated MTJ elements, the lines extending in the Xdirection, and the lines extending in the Y direction are described tobe shifted from each other in each portion, respectively. But this isdirected for simplifying the description, and actually they may beshifted from each other, or may be fully overlapped.

{circle around (2)} Second Embodiment

FIG. 10 shows a cell array section of a magnetic random access memoryaccording to a second embodiment of the present invention.

The magnetic random access memory according to the present embodiment ischaracterized in that the number of accumulated portions of the MTJelements 10 of FIG. 8 is set to be four as compared with the magneticrandom access memory of FIG. 8, and other points are same as themagnetic random access memory of FIG. 8.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, four portions) on the semiconductorsubstrate. Further, the MTJ elements 10 construct the array in the X-Yplane in each portion.

The upper line 11 and the lower line 12 both extend in the X direction,and a plurality of MTJ elements 10 arranged in the X direction arearranged between both the lines 11 and 12. The selective transistor 14is connected to one end of the upper line 11. The peripheral circuitsuch as the sense amplifier (S/A) 15 is connected to one end of thelower line 12.

The upper line 11 and the lower line 12 each function as a read line. Inother words, the read current flows in the path from the upper line 11through the MTJ elements 10 to the lower line 12, that is along the Xdirection during data reading.

The write lines 13 are arranged above the MTJ elements 10 and extend inthe Y direction in each portion of the array of the MTJ elements 10.Further, the write lines 13 are arranged in the vicinity of the freelayers of the MTJ elements 10. Moreover, when a group of a plurality ofMTJ elements arranged in the X direction is assumed to be one column anda group of a plurality of MTJ elements arranged in the Y direction isassumed to be one row, in the present embodiment, the write lines 13arranged in each portion are connected in serial in one row of the arrayof the MTJ elements 10.

More specifically, as shown in FIG. 11, the write line 13 in the upperportion and the write line 13 in the lower portion are electricallyconnected to each other via the contact plugs at the end of the array ofthe MTJ elements 10. In FIG. 11, the upper lines and the lower lines areomitted for simplicity.

In the present embodiment, the number of accumulated portions of the MTJelements 10 is four. That is, when the number of accumulated portions ofthe MTJ elements 10 is even number (2, 4, 6, . . . portions), twocontact sections for connecting the write lines 13 and the transistorsare both arranged at one end of the array section of the MTJ elements 10as shown in FIG. 11.

In this case, for example, as shown in FIG. 11, the transistor connectedto one end of the write line 13 in the block BK0 is arranged immediatelybelow the array of the block BK1 adjacent to the block BK0, and thetransistor connected to the other end of the write line 13 in the blockBK0 is arranged immediately below the array of the block BK0.

As with the aforementioned first embodiment, when the number ofaccumulated portions of the MTJ elements 10 is odd number (3, 5, 7, . .. portions), as shown in FIG. 9, the contact section for connecting oneend of the write line 13 and the transistor is arranged at one end ofthe array section of the MTJ elements 10. The contact section forconnecting the other end of the write line 13 and the transistor isarranged at the other end opposite to the one end of the array sectionof the MTJ elements 10.

Therefore, in this case, for example, as shown in FIG. 9, thetransistors connected to one end and the other end of the write line 13in the block BK0 are arranged immediately below the array of the blockBK0, respectively.

As described above, in the present embodiment, the lines having the samefunction arranged in each portion, that is the write lines are connectedin serial in one row of the array of the MTJ elements 10 so that thetransistors may be arranged by one transistor at both ends of the writeline. Therefore, the number of transistors arranged at the end of thearray of the MTJ elements 10 can be remarkably reduced.

Further, according to such a device structure, the transistor may beconnected to the line connected in serial in one row of the array of theMTJ elements 10 irrespective of the number of accumulated portions ofthe MTJ elements. Therefore, even when the number of accumulatedportions of the MTJ elements 10 is increased so that the increase in thememory capacity is achieved, the number of transistors is not increasedand the layout thereof does not become complicated.

Moreover, since the number of transistors connected to the write lines13 arranged in each portion in one row of the array of the MTJ elements10 is always constant, assuming that the array of the MTJ elements 10 isone small block, a large memory cell array may be constructed by aplurality of blocks. In this case, for example, as shown in FIG. 11, thecore circuits such as the transistors or sense amplifiers may bearranged immediately below the MTJ elements 10 in each block.

{circle around (3)} Third Embodiment

FIG. 12 shows a cell array section of a magnetic random access memoryaccording to a third embodiment of the present invention.

The magnetic random access memory according to the present embodiment ischaracterized in that the orientation of magnetization of the pin layersof the MTJ elements 10 of FIG. 10 is changed every portion, and otherpoints are same as the magnetic random access memory of FIG. 10.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, four portions) on the semiconductorsubstrate. Further, the MTJ elements 10 construct the array in the X-Yplane in each portion.

The upper line 11 and the lower line 12 both extend in the X direction,and a plurality of MTJ elements 10 arranged in the X direction arearranged between both the lines 11 and 12. The selective transistor 14is connected to one end of the upper line 11. Further, the peripheralcircuit such as the sense amplifier (S/A) 15 is connected to one end ofthe lower line 12.

The upper line 11 and the lower line 12 each function as a read line. Inother words, the read current flows in the path from the upper line 11through the MTJ elements 10 to the lower line 12, that is along the Xdirection during data reading.

The write lines 13 are arranged above the MTJ elements 10 and extend inthe Y direction in each portion of the array of the MTJ elements 10.Further, the write lines 13 are arranged in the vicinity of the freelayers of the TMT elements 10. Moreover, when a group of a plurality ofMTJ elements arranged in the X direction is assumed to be one column anda group of a plurality of MTJ elements arranged in the Y direction isassumed to be one row, in the present embodiment, the write lines 13arranged in each portion are connected in serial in one row of the arrayof the MTJ elements 10.

That is, as shown in FIG. 11, the write line 13 in the upper portion andthe write line 13 in the lower portion are electrically connected toeach other via the contact plugs at the end of the array of the MTJelements 10.

In the aforementioned second embodiment, the write lines 13 are arrangedin a meandering manner in the Y-Z plane as clear from FIG. 11. In thiscase, as shown in FIG. 12, when the current in one direction is flowedthrough the write lines 13, the orientation of the current flowingthrough the write lines 13 in each portion is reverse every portion.

In the case of FIG. 12, the write current directing from recto to versoflows through the write lines at the odd portions, that is the writelines 13 at the first portion nearest to the semiconductor substrate andthe write lines 13 at the third portion, and the write current directingfrom verso to recto flows through the write lines 13 in the evenportions, that is the write lines in the second and fourth portions.

In such a situation, for example, assuming that the orientations of themagnetization of the pin layers of all the MTJ elements 10 are same, forexample, when the same data is written into the MTJ elements in the oddportions and the MTJ elements in the even portions, the write current ina different direction has to be flowed through the write lines 13.

In other words, in the case where the orientations of the magnetizationof the pin layers of all the MTJ elements 10 are same and theorientation of the write current of the lower lines 12 is constant, whenonly the write current in one direction is flowed through the writelines 13, the orientation of the magnetization of the free layers of theMTJ elements 10 in each portion is reverse every portion. That is, themagnetization state of the MTJ elements 10 in each portion is parallelor anti-parallel every portion so that different data is written intothe MTJ elements 10 in each portion in spite of the same operation.

As described above, in the second embodiment, when the current in onedirection is flowed through the write lines 13, the orientation of thecurrent flowing through the write lines 13 is reverse to each otherevery portion so that a method of controlling the write operation may becomplicated.

In the present embodiment, in order to solve such a problem, as shown inFIG. 12, it is proposed that the orientation of the magnetization of thepin layers of the MTJ elements 10 is changed every portion. In thiscase, when only the write current in one direction is flowed through thewrite lines 13, the orientation of the magnetization of the free layersof the MTJ elements 10 in each portion is reverse every portion, but themagnetization state of the MTJ elements 10 in each portion is same(parallel or anti-parallel) by each portion. That is, the same data iswritten into the MTJ elements 10 in each portion.

The orientation of the magnetization of the pin layers of the MTJelements 10 can be easily changed every portion according to aconventional process. In other words, in order to change the orientationof the magnetization of the pin layers of the MTJ elements 10 everyportion, the orientation of the magnetic fields only has to be adjustedwhen materials constructing the pin layers are deposited.

In the present embodiment, the problem that the write lines 13 arearranged in the meandering manner is solved by changing the orientationof the magnetization of the pin layers of the MTJ elements 10 everyportion, but there are some solving methods other than this method.

For example, as described above, the current in a different directionmay be flowed through the write lines 13 or the orientation of the writecurrent flowed through the lower lines 12 may be changed though thewrite control is complicated. Further, it is permitted that the samedata is saved in a different magnetization state in each portion so thatthe condition of data determination may be changed every portion.

As described above, in the present embodiment, the orientation of themagnetization of the pin layers of the MTJ elements is changed everyportion. In this case, when only the write current in one direction isflowed through the write lines, the orientation of the magnetization ofthe free layers of the MTJ elements in each portion is reverse everyportion, but the magnetization state of the MTJ elements in each portionis same (parallel or anti-parallel) by each portion.

Therefore, according to the present embodiment, the same effect as themagnetic random access memory according to the aforementioned secondembodiment can be obtained and the method of controlling the writeoperation does not become complicated.

{circle around (4)} Fourth Embodiment

FIG. 13 shows an outline of a cell array section of a magnetic randomaccess memory according to a fourth embodiment of the present invention.In FIG. 13, the upper lines and the lower lines connected to the MTJelements are omitted for simplicity.

The magnetic random access memory according to the present embodiment ischaracterized in that the write lines 13 arranged in each portion of theMTJ elements 10 of FIG. 11 are connected not in serial but in parallelas compared with the magnetic random access memory of FIG. 11, and otherpoints are same as the magnetic random access memory of FIG. 11.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, four portions) on the semiconductorsubstrate. Further, the MTJ elements 10 construct the array in the X-Yplane in each portion.

Also in the present embodiment, as shown in FIG. 10, the upper line 11and the lower line 12 both extend in the X direction, and a plurality ofMTJ elements 10 arranged in the X direction are arranged between boththe lines 11 and 12. The selective transistor 14 is connected to one endof the upper line 11. Further, the peripheral circuit such as the senseamplifier (S/A) 15 is connected to one end of the lower line 12.

As shown in FIG. 13, the write lines 13 are arranged above the MTJelements 10 and extend in the Y direction in each portion of the arrayof the MTJ elements 10. Further, the write lines 13 are arranged in thevicinity of the free layers of the MTJ elements 10. Moreover, when agroup of a plurality of MTJ elements arranged in the X direction isassumed to be one column and a group of a plurality of MTJ elementsarranged in the Y direction is assumed to be one row, in the presentembodiment, the write lines 13 arranged in each portion are connected inparallel in one row of the array of the MTJ elements 10.

In other words, the write line 13 in the upper portion and the writeline 13 in the lower portion are electrically connected to each othervia the contact plugs at the end of the array of the MTJ elements 10.

In the aforementioned second embodiment, the write lines 13 in eachportion are connected in serial to each other so that the write lines 13are arranged in the meandering manner in the Y-Z plane as clear fromFIG. 11. On the contrary, in the present embodiment, the write lines 13in each portion are connected in parallel to each other so that thewrite lines are arranged in a ladder shape in the Y-Z plane as clearfrom FIG. 13.

In the present embodiment, when the current in one direction is flowedthrough the write lines 13, the orientations of the current flowingthrough the write lines 13 in the respective portions are identical toeach other unlike the second embodiment.

Therefore, according to the present embodiment, the same effect as themagnetic random access memory according to the aforementioned secondembodiment can be obtained, and the write operation can be easilycontrolled even when the measures that the orientation of themagnetization of the pin layers of the MTJ elements is changed everyportion are not taken as with the aforementioned third embodiment.

Further, in the present embodiment, since the write lines in eachportion are connected in parallel, the contact sections between thewrite lines and the transistors are arranged by one contact section attwo ends opposite to each other of the array of the MTJ elements.Therefore, assuming that the array of the MTJ elements is one smallblock, a large memory cell array may be configured with a plurality ofblocks. In this case, the core circuits such as the transistors or senseamplifiers may be arranged immediately below the MTJ elements in eachblock.

{circle around (5)} Fifth Embodiment

FIG. 14 shows a cell array section of a magnetic random access memoryaccording to a fifth embodiment of the present invention. FIG. 15 showsa section along the Y direction of the cell array section of FIG. 14.

The fifth embodiment is an example in combination with theaforementioned first embodiment and the “sharing of wiring”.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, four portions) on the semiconductorsubstrate. Further, the MTJ elements 10 construct the array in the X-Yplane in each portion.

The write line 13 is arranged between two MTJ elements 10 adjacent inthe vertical direction, and extends in the Y direction. In the presentembodiment, the write line 13 is shared with two MTJ elements adjacentin the vertical direction. In other words, the write lines 13 are notarranged between all the portions, but are arranged, for example,immediately above the MTJ elements 10 in the odd portions andimmediately below the MTJ elements 10 in the even portions from thesemiconductor substrate side.

Further, when a group of a plurality of MTJ elements arranged in the Xdirection is assumed to be one column and a group of a plurality of MTJelements arranged in the Y direction is assumed to be one row, in thepresent embodiment, the write lines 13 arranged in each portion areconnected in serial in one row of the array of the MTJ elements 10.

In addition, two MTJ elements above and below the write line 13 arearranged symmetric to each other relative to the write line 13. That is,the pin layer in which the orientation of the spin is pinned of the twomagnetic layers of the MTJ element 10 is arranged far away from thewrite line 13. Moreover, the free layer in which the orientation of thespin can be freely changed of the two magnetic layers of the MTJ element10 is arranged near the write line 13. The write line 13 is positionedequidistantly from the two MTJ elements 10 above and below the writeline 13 and is separated from the two MTJ elements 10.

In each portion, the first conductive line 11A functioning as a readline is connected to the pin layer of the MTJ element 10. The conductiveline 11A extends in the X direction, and is commonly connected to thepin layers of a plurality of MTJ elements 10 arranged in the Xdirection. The sense amplifier (S/A) 15 is connected to one end of thefirst conductive line 11A.

Further, in each portion, the second conductive line 12A functioning asa write line and read line is connected to the free layer of the MTJelement 10. The second conductive line 12A extends in the X direction,and is commonly connected to the free layers of a plurality of MTJelements 10 arranged in the X direction. The switching element 14functioning as a selective transistor is connected to one end of thesecond conductive line 12A.

According to such a cell structure of the fifth embodiment, the sameeffect as the first embodiment can be obtained and the effect withrespect to the aforementioned “sharing of wiring” can be obtained.

{circle around (6)} Sixth Embodiment

FIG. 16 shows a cell array section of a magnetic random access memoryaccording to a sixth embodiment of the present invention.

The sixth embodiment is an example in which a plurality of MTJ elementsaccumulated in a plurality of portions present in one column arecollectively connected to one sense amplifier.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, four portions) on the semiconductorsubstrate. Further, the MTJ elements 10 construct the array in the X-Yplane in each portion.

The write line 13 is arranged between two MTJ elements 10 adjacent inthe vertical direction, and extends in the Y direction. In the presentembodiment, the write line 13 is shared with two MTJ elements adjacentin the vertical direction. In other words, the write lines 13 are notarranged between all the portions, are arranged, for example,immediately above the MTJ elements 10 in the odd portions andimmediately below the MTJ elements 10 in the even portions from thesemiconductor substrate side.

Further, two MTJ elements present above and below the write line 13 arearranged symmetric to each other relative to the write line 13. That is,the pin layer in which the orientation of the spin is pinned of the twomagnetic layers of the MTJ element 10 is arranged far away from thewrite line 13. In addition, the free layer in which the orientation ofthe spin can be freely changed of the two magnetic layers of the MTJelement 10 is arranged near the write line 13. The write line 13 ispositioned equidistantly from the two MTJ elements 10 present above andbelow the write line 13, and is separated from the two MTJ elements 10.

In each portion, the first conductive line 11A functioning as a readline is connected to the pin layer of the MTJ element 10. The firstconductive line 11A extends in the X direction, and is commonlyconnected to the pin layers of a plurality of MTJ elements 10 arrangedin the X direction.

In the present embodiment, when a group of a plurality of MTJ elementsarranged in the X direction is assumed to be one column, in one columnof the array of the MTJ elements 10, one ends of the first conductivelines 11A arranged in each portion are commonly connected. The commonlyconnected first conductive lines 11A are connected to the senseamplifier (S/A) 15.

Further, in each portion, the second conductive line 12A functioning asa write line and read line is connected to the free layer of the MTJelement 10. The second conductive line 12A extends in the X direction,and is commonly connected to the free layers of a plurality of MTJelements 10 arranged in the X direction.

In the present embodiment, in one column of the array of the MTJelements 10, the second conductive lines 12A arranged in each portionare commonly connected at one ends thereof. The second conductive lines12A are connected to the switching element 14 functioning as a selectivetransistor.

As described above, in the cell structure according to the sixthembodiment, one ends of the first conductive lines 11A are commonlyconnected and the connecting points thereof are connected to one senseamplifier S/A. Further, one ends of the second conductive lines 12A arecommonly connected, and the connecting points thereof are connected toone switching element 14.

Also in such a structure, the same effect as the first embodiment, forexample, the effect that the number of transistors arranged on theperiphery of the memory cell array is decreased can be obtained.Further, in the present embodiment, the effect with respect to theaforementioned “sharing of wiring” can be obtained.

(4) Others

In the first to fifth embodiments, there is described a case where thewrite lines (write-only lines) arranged in each portion in one row areconnected in serial or in parallel in the array structure in which theMTJ elements are accumulated in a plurality of portions. However, thepresent invention can be applied to the lines arranged in the array ofthe MTJ elements other than the write lines.

For example, as with the sixth embodiment, the present invention can beapplied to the upper lines 11 and the lower lines 12 in FIG. 1, and theupper lines 11 and the lower lines 12 in FIG. 2, respectively.

Further, in the first to fourth embodiments, the lines arranged in eachportion of the MTJ elements accumulated in a plurality of portions aredescribed by way of example. But, for example, in the case where theline is shared with the upper and lower MTJ elements, the lines havingthe same function are arranged not in each portion but every otherportion.

Also in such a case, as shown in the fifth embodiment, the linesarranged every other portion can be connected in serial or in parallelto construct the present invention.

Furthermore, in the first to fourth embodiments, the transistorsconnected to the lines in the array of the MTJ elements are generallyMOS transistors, but may be bipolar transistors, diodes, or the like.

In the present invention, the magnetic random access memory having anarray structure in which the MTJ elements are accumulated in a pluralityof portions can be applied to any devices having any structure.

(5) Conclusion

Hereinbefore, as described above, according to the magnetic randomaccess memory of the embodiments of the present invention, theconductive lines having the same function arranged in each portion areconnected in serial or in parallel in the array structure in which theMTJ elements are accumulated in a plurality of portions. Accordingly,the transistors may be arranged by one transistor at one ends or bothends of the conductive lines so that it is possible to decrease thenumber of transistors arranged at the end of the array of the MTJelements.

Further, the transistors may be connected to the conductive linesconnected in serial or in parallel in one row or column of the array ofthe MTJ elements irrespective of the number of accumulated portions ofthe MTJ elements. Therefore, even when the number of accumulatedportions of the MTJ elements is increased so that the increase in thememory capacity is achieved, the number of transistors is not increasedand the layout thereof does not become complicated.

Moreover, since the number of transistors connected to the conductivelines arranged in one column of the array of the MTJ elements isconstant, assuming that the array of the MTJ elements is one smallblock, a large memory cell array may be constructed by a plurality ofblocks. In this case, the core circuits such as the transistors or senseamplifiers may be arranged immediately below the MTJ elements.

3. Three-Dimensional Wiring

(1) Presupposed Technique

FIGS. 17 and 18 show a presupposed technique of a magnetic random accessmemory according to embodiments of the present invention.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, three portions) on thesemiconductor substrate. Further, in each portion, a plurality of MTJelements 10 are connected in parallel between the upper line 11 and thelower line 12.

The upper line 11 extends in the X direction, and one end thereof isconnected to the selective transistor 14. The lower line 12 also extendsin the X direction, and one end thereof is connected to the peripheralcircuit such as the sense amplifier (S/A) 15. In the present embodiment,the read current flows in the path from the upper line 11 through theMTJ elements 10 to the lower line 12, that is along the X direction. Thewrite lines 13 are arranged adjacent to the MTJ elements 10, and extendin the Y direction.

FIGS. 19 and 20 show an example in which the lower line and the writeline are integrated in the cell, structure in FIGS. 17 and 18.

The lower line 12 extends in the Y direction, and one end thereof isconnected to the sense amplifiers (S/A). The lower line 12 functions asa write line during writing. The lower line 12 functions as a read lineduring reading. The read current flows through the upper line (Xdirection) 11 at first, and then flows through the MTJ elements 10 tothe lower line (Y direction) 12.

A basic structure of the magnetic random access memory is a 1 cell-1transistor structure in which one switching element (selectivetransistor) is corresponded to one MTJ element. However, in the devicestructure in which the MTJ elements are accumulated in a plurality ofportions, when one switching element is corresponded to one MTJ element,the number of switching elements is increased, which is disadvantageousfor the high density of the cells.

In the case of the device structure in which the MTJ elements 10 areaccumulated in a plurality of portions, there is employed the devicestructure in which read operation or write operation can be performedeven when one switching element is not corresponded to one MTJ element.

For example, in the device structure shown in FIGS. 17 to 20, in eachportion of the array of the MTJ elements 10, a plurality of MTJ elements10 are connected between the upper line 11 and the lower line 12. Forexample, the selective transistor 14 is connected to one end of theupper line 11, and the sense amplifier (S/A) 15 is connected to one endof the lower line 12.

However, in this case, in the example of FIGS. 17 and 18, three lines ofthe upper line (read/write line) 11, the lower line (read line) 12 andthe write line 13 in total have to be arranged in each portion of thearray of the MTJ elements 10. Further, in the example in FIGS. 19 and20, two lines of the upper line (read/write line) 11 and the lower line(read/write line) 12 in total have to be arranged in each portion of thearray of the MTJ elements 10.

When such a write line or read line (current path line) is arranged inthe array of the MTJ elements accumulated in a plurality of portions onthe substrate, when the number of accumulated portions of the MTJelements becomes larger, the device structure becomes complicated sothat the following problems occur.

a. The characteristics of the MTJ elements are largely influenced by theflatness of the surfaces (base films) on which the MTJ elements arearranged. Since this flatness is deteriorated when the number ofaccumulated portions of the MTJ elements becomes larger, deteriorationof the characteristics of the MTJ elements occurs along with theincrease in the number of accumulated portions of the MTJ elements.

b. When the data write/read operation for the MTJ element is performedusing three or more lines (for example, FIGS. 17 and 18), one read lineand one write line have to be insulated from each other and the readline has to be in contact with the MTJ element. In other words, onewrite line is extra separated from the MTJ element by the thickness ofone read line.

It is a well-known fact that the intensity of the magnetic fieldgenerated by the current flowed through the write line is inverselyproportional to square of the distance. Therefore, as described above,when three or more lines are used, the distance between one write lineand the MTJ element becomes larger, and the variations thereof are alsoincreased. That is, the variations of the magnetic field given to theMTJ element by the current flowed through the write line are increasedso that sufficient margin has to be secured with respect to the magneticfield required for writing.

c. The transistors are connected to the respective ends of theconductive lines arranged in each portion of the array of the MTJelements. Further, the conductive lines extend in the X direction or theY direction on the array of the MTJ elements. Therefore, the transistorsconnected to the conductive lines are intensively arranged in the areasat the end of the array (or on the periphery of the array) (refer toFIG. 6).

On the other hand, in the data write/read operation for the MTJelements, it is known that a large current is required due to thecharacteristics of the MTJ elements. Therefore, the size (or pitch) ofthe transistors connected to the lines inevitably becomes larger.

Accordingly, when the number of accumulated portions of the MTJ elementsis increased, the number of transistors which have to be arranged in onerow or column is increased in proportion thereto. Consequently, all thetransistor cannot be arranged at the periphery of the array, or thepitch of the MTJ elements is influenced by the pitch of the transistorsso that high integration of the MTJ elements cannot be achieved.

(2) Outline

The embodiments of the present invention (three-dimensional wiring) areapplied to a magnetic random access memory having an array structure inwhich the MTJ elements are accumulated in a plurality of portions.

The magnetic random access memory according to the embodiments of thepresent invention is characterized in that a plurality of lines used fordata writing/reading are three-dimensionally arranged in the array ofthe MTJ elements.

In other words, conventionally, all the lines used for the datawriting/reading extend in the X direction or the Y direction. On thecontrary, in the magnetic random access memory according to theembodiments of the present invention, assuming that the direction inwhich the MTJ elements are accumulated in a plurality of portions is theZ-axis direction, when the MTJ elements construct the array in the X-Yaxis directions in each portion, at least one of a plurality ofconductive lines used for the data writing/reading is extended in theZ-axis direction.

As described above, the conductive lines used for the datawriting/reading are three-dimensionally arranged so that the number ofconductive lines extending in the X-Y axis directions can be decreased.The conductive lines extending in the Z-axis direction can be easilyformed by, for example, a contact process. From the above, even when thenumber of accumulated portions of the MTJ elements is increased, it ispossible to realize improvement of the flatness of the base films andimprovement of the characteristics of the MTJ elements.

Further, when the conductive lines used for the data writing/reading arethree-dimensionally arranged, the degree of freedom of the layout of theconductive lines in the array is increased so that, for example, twowrite lines can be arranged in the vicinity of the MTJ elements and thevariations of the magnetic fields given to the MTJ elements can berestricted.

Moreover, one end of the conductive line extending in the Z-axisdirection is present immediately below the array of the MTJ elements.Therefore, the transistor connected to the conductive line can be easilyformed immediately below the array so that the transistors are notconcentrated on the periphery of the array.

(3) Embodiments

{circle around (1)} First Embodiment

FIG. 21 shows a layout of a cell array section of a magnetic randomaccess memory according to a first embodiment of the present invention.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, three portions) on thesemiconductor substrate. Further, the MTJ elements 10 construct thearray in the X-Y plane in each portion.

The upper line 11 functions as a read line, and extends in the Xdirection. The upper line 11 is in contact with, for example, the freelayers of the MTJ elements 10. The lower line 12 functions as a readline and write line, and extends in the Y direction. The lower line 12is in contact with, for example, the pin layers of the MTJ elements 10.Further, for example the selective transistor is connected to one end ofthe upper line 11, and the sense amplifier (S/A) is connected to one endof the lower line 12.

The write line 13 extends in the Z-axis direction, and is arranged inthe vicinity of a plurality of MTJ elements 10 accumulated in the Z-axisdirection. The data to be written in the MTJ element 10 (the orientationof the magnetization of the free layer) is determined by the syntheticmagnetic field of the magnetic field generated by the current flowingthrough the lower line 12 in the Y-axis direction and the magnetic fieldgenerated by the current flowing through the write line 13 in the Z-axisdirection.

The selective transistor (for example, MOS transistor) 14 is connectedto one end of the write line 13 at the substrate side. This selectivetransistor 14 is arranged immediately below the array of the MTJelements 10.

According to such a device structure, at least one (in the presentembodiment, the write line 13) of a plurality of conductive lines usedfor the data writing/reading is extended in the Z-axis direction.

For example, with respect to a case where writing/reading is performedusing three conductive lines, conventionally, since all the threeconductive lines extend in the X-axis direction or the Y-axis direction,at least three multilayer wiring processes are required for one portionof the array of the MTJ elements. On the contrary, in the example of thepresent invention, the conductive line extending in the Z-axis directioncan be formed by the contact process so that it is possible to decreasethe number of multilayer wiring processes per portion of the array ofthe MTJ elements.

Thereby, even when the number of accumulated portions of the MTJelements is increased, the improvement of the flatness of the base filmsand the improvement of the characteristics of the MTJ elements can berealized.

Further, when the conductive lines used for the data writing/reading arethree-dimensionally arranged, the degree of freedom of the layout of thelines in the array is increased.

For example, with respect to a case where writing/reading is performedusing three lines, conventionally, there is employed a structure wherethe read line is arranged between the write-only conductive line and theMTJ element so that the distance between the write-only conductive lineand the MTJ element becomes larger. On the contrary, in the example ofthe present invention, for example, the write-only conductive line isextended in the Z-axis direction. In this way, this write-onlyconductive line can be arranged in the vicinity of the MTJ element sothat the variations of the magnetic field given to the MTJ element canbe restricted.

In addition, one end of the write line extending in the Z-axis directionis present immediately below the array of the MTJ elements. Therefore,the transistor connected to the conductive line can be easily formedimmediately below the array so that concentration of the transistors onthe periphery of the array can be alleviated.

In the present embodiment, a device structure is employed in which threetypes of conductive lines are arranged in the array of the MTJ elementsand the respective lines are orthogonal to each other and extend in thedifferent directions from each other. By doing so, the transistorsconnected to the respective lines can be arranged in a dispersed manneron the substrate.

In the present invention, it is enough that at least one conductive lineextending in the Z direction is present. When a plurality of conductivelines other than this line are provided, they may extend in the samedirection or in the different directions from each other.

{circle around (2)} Second Embodiment

In the aforementioned first embodiment, there is described the casewhere the three types of conductive lines are arranged in the array ofthe MTJ elements, but the present invention can be applied to a casewhere only two types of conductive lines having the function as aread/write line are arranged in the array of the MTJ elements.

FIG. 22 shows a layout of a cell array section of a magnetic randomaccess memory according to a second embodiment of the present invention.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, three portions) on thesemiconductor substrate. Further, the MTJ elements 10 construct thearray in the X-Y plane in each portion.

Conductive patterns 11C are formed on the MTJ elements 10. Theconductive line 13 functioning as a write line and read line (currentpath line) extends in the Z-axis direction, and is arranged in thevicinity of a plurality of MTJ elements 10 accumulated in the Z-axisdirection. Further, the conductive line 13 is connected to theconductive patterns 11C of a plurality of MTJ elements 10 accumulated inthe Z-axis direction.

The selective transistor (for example, MOS transistor) 14 is connectedto one end of the conductive line 13 at the substrate side. Thisselective transistor 14 is arranged immediately below the array of theMTJ elements 10.

The lower line 12 functions as a write line and read line (current pathline), and extends in the Y direction. The lower line 12 is in contactwith, for example, the pin layers of the MTJ elements 10. Further, forexample, the sense amplifier (S/A) is connected to one end of the lowerline 12.

The data to be written in the MTJ element 10 (the orientation of themagnetization of the free layer) is determined by the synthetic magneticfield of the magnetic field generated by the current flowing through thelower line 12 in the Y-axis direction and the magnetic field generatedby the current flowing through the write line 13 in the Z-axisdirection.

According to such a device structure, at least one (in the presentembodiment, the conductive line 13) of a plurality of conductive linesused for the data writing/reading is extended in the Z-axis direction.The conductive line extending in the Z-axis direction can be formed bythe contact process so that it is possible to decrease the number ofmultilayer wiring processes per portion of the array of the MTJelements.

In the present embodiment, in each portion of the array of the MTJelements, only one conductive line extends in the X direction or the Ydirection so that the improvement of the flatness of the base films andthe improvement of the characteristics of the MTJ elements can befurther achieved.

Further, when the conductive lines used for the data writing/reading arethree-dimensionally arranged, the degree of freedom of the layout of theconductive lines in the array can be increased and the variations of themagnetic fields given to the MTJ elements can be restricted.

Furthermore, one end of the write line extending in the Z-axis directionis arranged immediately below the array of the MTJ elements. In otherwords, the transistor connected to the conductive line is arrangedimmediately below the array of the MTJ elements so that theconcentration of the transistors on the periphery of the array can bealleviated.

{circle around (3)} Third Embodiment

The present embodiment is a modified example of the magnetic randomaccess memory according to the aforementioned first embodiment.

In the aforementioned first embodiment, in one portion of the array ofthe MTJ elements, one write line is corresponded to one MTJ element.However, in the present embodiment, in one portion of the array of theMTJ elements, a configuration is employed in which one write line iscorresponded to two MTJ elements adjacent in the X direction. In otherwords, in one portion of the array of the MTJ elements, one write lineis sandwiched by the two MTJ elements.

Such a structure makes it possible to reduce the number of write linesextending in the Z-axis direction to half the number required for theaforementioned first embodiment so that high density of the MTJ elementscan be accordingly realized.

FIG. 23 shows a layout of a cell array section of a magnetic randomaccess memory according to a third embodiment of the present invention.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the embodiment, three portions) on the semiconductorsubstrate. Further, the MTJ elements 10 construct the array in the X-Yplane in each portion.

The upper line 11 functions as a read line, and extends in the Xdirection. The upper line 11 is in contact with, for example, the freelayers of the MTJ elements 10. The lower line 12 functions as a writeline and read line, and extends in the Y direction. The lower line 12 isin contact with, for example, the pin layers of the MTJ elements 10.Further, for example, the selective transistor is connected to one endof the upper line 11, and the sense amplifier (S/A) is connected to oneend of the lower line 12.

The write line 13 extends in the Z-axis direction, and is arranged inthe vicinity of a plurality of MTJ elements 10 accumulated in the Z-axisdirection.

Further, in the present embodiment, in one portion of the array of theMTJ elements 10, one write line 13 is corresponded to two MTJ elementsadjacent in the X direction. In other words, in one portion of the arrayof the MTJ elements, one write line 13 is sandwiched by the two MTJelements.

With such a structure, the number of write lines 13 extending in theZ-axis direction can be decreased so that the high density of the MTJelements can be accordingly realized.

The selective transistor (for example, MOS transistor) 14 is connectedto one end of the write line 13 at the substrate side. The selectivetransistor 14 is arranged immediately below the array of the MTJelements 10.

The data to be written in the MTJ element 10 (the orientation of themagnetization of the free layer) is determined by the synthetic magneticfield of the magnetic field generated by the current flowing through thelower line 12 in the Y-axis direction and the magnetic field generatedby the current flowing through the write line 13 in the Z-axisdirection.

Here, in the present embodiment, when the current in one direction isflowed through the write line 13, as shown in FIG. 26, in one portion ofthe array of the MTJ elements 10, the orientation a1 of the magneticfield given to the MTJ element present at the left side of the writeline 13 and the orientation a2 of the magnetic field given to the MTJelement present at the right side thereof are reverse to each other.

Therefore, with respect to the same write operation, the magnetizationstates of the two MTJ elements present at the right and left sides ofthe write line 13 are different from each other.

That is, in this case, assuming that the data stored in the two MTJelements is same, it is required that the condition of “1”/“0”determination when reading the data stored in the MTJ element at theleft side of the write line 13 and the condition of “1”/“0”determination when reading the data stored in the MTJ element at theright side of the write line 13 are reverse to each other.

According to such a device structure, at least one (in the presentembodiment, the write line 13) of a plurality of conductive lines usedfor the data writing/reading is extended in the Z-axis direction. Inother words, the conductive line extending in the Z-axis direction canbe formed by the contact process, thereby capable of decreasing thenumber of multilayer wiring processes per portion of the array of theMTJ elements.

Accordingly, even when the number of accumulated portions of the MTJelements is increased, the improvement of the flatness of the base filmsand the improvement of the characteristics of the MTJ elements can berealized.

Further, when the conductive lines used for the data writing/reading arethree-dimensionally arranged, the degree of freedom of the layout of theconductive lines in the array can be increased. Furthermore, forexample, when the write-only conductive line is extended in the Z-axisdirection, this write-only conductive line can be arranged in thevicinity of the MTJ elements so that the variations of the magneticfields given to the MTJ elements can be restricted.

In addition, one end of the write line extending in the Z-axis directionis present immediately below the array of the MTJ elements. Therefore,the transistor connected to the conductive line can be easily formedimmediately below the array so that the concentration of the transistorson the periphery of the array can be alleviated.

In the present embodiment, in one portion of the array of the MTJelements, one write line is corresponded to two MTJ elements adjacent inthe X direction. That is, in one portion of the array of the MTJelements, one write line is sandwiched by the two MTJ elements. Such astructure makes it possible to decrease the number of write linesextending in the Z-axis direction so that the high density of the MTJelements can be accordingly realized.

In the present embodiment, a device structure is employed in which threetypes of conductive lines are arranged in the array of the MTJ elementsand the respective lines are orthogonal to each other and extend in thedifferent directions from each other. By doing so, the transistorsconnected to the respective lines can be arranged in a dispersed manneron the substrate.

However, in the present invention, it is enough that at least oneconductive line extending in the Z direction is present. When aplurality of other conductive lines are present, they may extend in thesame direction or in the different directions from each other.

{circle around (4)} Fourth Embodiment

In the aforementioned third embodiment, there is described the magneticrandom access memory when the three types of the conductive lines arearranged in the array of the MTJ elements. In the present embodiment,there will be described a magnetic random access memory in which onlytwo types of conductive lines having the same function as a read/writeline are arranged in the array of the MTJ elements.

FIG. 24 shows a layout of a cell array section of a magnetic randomaccess memory according to a fourth embodiment of the present invention.

A plurality of MTJ elements 10 are arranged in a plurality of portions(in the present embodiment, only one portion is illustrated forsimplicity) on the semiconductor substrate. Further, the MTJ elements 10construct the array in the X-Y plane in each portion.

The conductive patterns 11C are formed on the MTJ elements 10. Theconductive line 13 functioning as a write line and read line (currentpath line) extends in the Z-axis direction, and is arranged in thevicinity of a plurality of MTJ elements 10 accumulated in the Z-axisdirection. In addition, the conductive line 13 is connected to theconductive patterns 11C of a plurality of MTJ elements 10 accumulated inthe Z-axis direction.

Moreover, in the present embodiment, in one portion of the array of theMTJ elements 10, one write line 13 is corresponded to two MTJ elementsadjacent in the X direction. In other words, in one portion of the arrayof the MTJ elements, one write line 13 is sandwiched by the two MTJelements.

With such a structure, the number of write lines 13 extending in theZ-axis direction can be decreased so that the high density of the MTJelements can be accordingly realized.

The selective transistor (for example, MOS transistor) 14 is connectedto one end of the conductive line 13 at the substrate side. Thisselective transistor 14 is arranged immediately below the array of theMTJ elements 10.

The lower line 12 functions as a write line and read line (current pathline), and extends in the Y direction. The lower line 12 is in contactwith, for example, the pin layers of the MTJ elements 10. Further, forexample, the sense amplifier (S/A) is connected to one end of the lowerline 12.

The data to be written in the MTJ element 10 (the orientation of themagnetization of the free layer) is determined by the synthetic magneticfield of the magnetic field generated by the current flowing through thelower line 12 in the Y-axis direction and the magnetic field generatedby the current flowing through the write line 13 in the Z-axisdirection.

According to such a device structure, at least one (in the presentembodiment, the conductive line 13) of a plurality of conductive linesused for the data writing/reading is extended in the Z-axis direction.The conductive line extending in the Z-axis direction can be formed bythe contact process so that the number of multilayer wiring processesper portion of the array of the MTJ elements can be decreased.

In the present embodiment, in each portion of the array of the MTJelements, only one conductive line extends in the X direction or the Ydirection so that the improvement of the flatness of the base films andthe improvement of the characteristics of the MTJ elements can befurther realized as compared with the aforementioned third embodiment.

Further, when the conductive lines used for data writing/reading arethree-dimensionally arranged, the degree of freedom of the layout of theconductive lines in the array can be increased and the variations of themagnetic fields given to the MTJ elements can be restricted.

Furthermore, one end of the write line extending in the Z-axis directionis arranged immediately below the array of the MTJ elements. In otherwords, the transistor connected to the conductive line is arrangedimmediately below the array of the MTJ elements so that theconcentration of the transistors on the periphery of the array can bealleviated.

In the present embodiment, in one portion of the array of the MTJelements, one write line is corresponded to two MTJ elements adjacent inthe X direction. That is, in one portion of the array of the MTJelements, one write line is sandwiched by the two MTJ elements. Such astructure allows to decrease the number of write lines extending in theZ-axis direction so that the high density of the MTJ elements can beaccordingly realized.

{circle around (5)} Fifth Embodiment

In the first to fourth embodiments described above, there is describedthe case where the write-only conductive line or the conductive linefunctioning as a read/write line is extended in the Z-axis direction.However, the present invention is characterized in that at least one ofa plurality of types of conductive lines arranged in the array of theMTJ elements is extended in the Z-axis direction.

In the present embodiment, there will be described a case where theread-only conductive line is extended in the Z-axis direction.

FIG. 25 shows a layout of a cell array section of a magnetic randomaccess memory according to a fifth embodiment of the present invention.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, only one portion is illustrated forsimplicity) on the semiconductor substrate. Further, the MTJ elements 10construct the array in the X-Y plane in each portion.

The conductive patterns 11C are formed on the MTJ elements 10. Theread-only line (current path line) 11 extends in the Z-axis direction,and is arranged in the vicinity of a plurality of MTJ elements 10accumulated in the Z-axis direction. Further, the read-only line 11 iscommonly connected to the conductive patterns 11C of a plurality of MTJelements 10 accumulated in the Z-axis direction.

Moreover, in the present embodiment, in one portion of the array of theMTJ elements 10, one read-only line 11 is corresponded to two MTJelements adjacent in the X direction. In other words, in one portion ofthe array of the MTJ elements, one read-only line 11 is sandwiched bythe two MTJ elements.

With such a structure, the number of read-only lines extending in theZ-axis direction can be decreased so that the high density of the MTJelements can be accordingly realized.

The selective transistor (for example, MOS transistor) 14 is connectedto one end of the read-only line 11 at the substrate side. Thisselective transistor 14 is arranged immediately below the array of theMTJ elements 10.

The write-only line 13 which is near but are not in contact with the MTJelements 10 is arranged above the MTJ elements 10. The write-only line13 extends in the X direction. The selective transistor is connected toone end or both ends of the write-only line 13.

The lower line 12 functions as a read line and write line, and extendsin the Y direction. The lower line 12 is in contact with, for example,the pin layers of the MTJ elements 10. Further, the sense amplifier(S/A) is connected to one end of the lower line 12.

The data to be written in the MTJ element 10 (the orientation of themagnetization of the free layer) is determined by the synthetic magneticfield of the magnetic field generated by the current flowing through thelower line 12 in the Y-axis direction and the magnetic field generatedby the current flowing through the write line 13 in the X-axisdirection.

According to such a device structure, at least one (in the presentembodiment, the read-only line 11) of a plurality of conductive linesused for the data writing/reading is extended in the Z-axis direction.That is, the line extending in the Z-axis direction can be formed by thecontact process, thereby capable of decreasing the number of multilayerwiring processes per portion of the array of the MTJ elements.

In this way, even when the number of accumulated portions of the MTJelements is increased, the improvement of the flatness of the base filmsand the improvement of the characteristics of the MTJ elements can berealized.

When the conductive lines used for data writing/reading arethree-dimensionally arranged, the degree of freedom of the layout of theconductive lines in the array can be increased. Further, for example,when the read-only conductive line is extended in the Z-axis direction,the write-only conductive line extending in the X direction can bearranged immediately above and in the vicinity of the MTJ elements sothat the variations of the magnetic fields given to the MTJ elements canbe restricted.

In addition, one end of the read-only line extending in the Z-axisdirection is present immediately below the array of the MTJ elements.Therefore, the transistor connected to the line can be easily formedimmediately below the array so that the concentration of the transistorson the periphery of the array can be alleviated.

In the present embodiment, in one portion of the array of the MTJelements, one read-only line is corresponded to two MTJ elementsadjacent in the X direction. In other words, in one portion of the arrayof the MTJ elements, one read-only line is sandwiched by the two MTJelements. With such a structure, the number of read-only lines extendingin the Z-axis direction can be decreased so that the high density of theMTJ elements can be accordingly realized.

{circle around (6)} Sixth Embodiment

FIG. 27 shows a layout of a cell array section of a magnetic randomaccess memory according to a sixth embodiment of the present invention.

A plurality of MTJ elements 10 are accumulated in a plurality ofportions (in the present embodiment, three portions) on thesemiconductor substrate. Further, the MTJ elements 10 construct thearray in the X-Y plane in each portion.

The upper line 11 functions as a read line and extends in the Xdirection. The upper line 11 is in contact with, for example, the freelayers of the MTJ elements 10. The lower line 12 functions as a readline and write line, and extends in the Y direction. The lower line 12is in contact with, for example, the pin layers of the MTJ elements 10.Further, for example, the selective transistor is connected to one endof the upper line 11, and the sense amplifier (S/A) is connected to oneend of the lower line 12.

The write line 13 extends in the Z-axis direction, and is arranged inthe vicinity of a plurality of MTJ elements 10 accumulated in the Z-axisdirection. The data to be written in the MTJ element 10 (the orientationof the magnetization of the free layer) is determined by the syntheticmagnetic field of the magnetic field generated by the current flowingthrough the lower line 12 in the Y-axis direction and the

1-67. (canceled)
 68. A magnetic random access memory comprising: a firstarray unit having a first magneto resistive element on a semiconductorsubstrate; a second array unit accumulated on the first array unit, thesecond array unit having a second magneto resistive element; and a firstconductive line as a write line through which a write current flows in awrite mode, which extends in a direction in which the first and secondarray units are accumulated, and which is adjacent to the first andsecond magneto resistive elements.
 69. The magnetic random access memoryaccording to claim 68, wherein the first array unit and the second arrayunit include only two types of conductive lines having functions as aread/write line.
 70. The magnetic random access memory according toclaim 68, wherein the first conductive line is shared with the first andsecond magneto resistive elements.
 71. The magnetic random access memoryaccording to claim 70, wherein the first conductive line is isolatedfrom the first and second magneto resistive elements.
 72. The magneticrandom access memory according to claim 70, wherein the first conductiveline is connected to the first and second magneto resistive elements inparallel.
 73. The magnetic random access memory according to claim 70,wherein the first conductive line functions only as the write line. 74.The magnetic random access memory according to claim 71, wherein thefirst conductive line functions also as a read line through which a readcurrent flows in a read mode.
 75. The magnetic random access memoryaccording to claim 68, further comprising: a second conductive lineprovided in the first array, which is orthogonal to the first conductiveline.
 76. The magnetic random access memory according to claim 75,wherein the first conductive line is isolated from the first and secondmagneto resistive elements, and the second conductive line is connectedto the first magneto resistive element.
 77. The magnetic random accessmemory according to claim 75, wherein the first and second conductivelines are connected to the first magneto resistive element.
 78. Themagnetic random access memory according to claim 75, wherein the firstand second conductive lines function as write lines.
 79. The magneticrandom access memory according to claim 75, further comprising: a thirdconductive line provided in the first array, which is orthogonal to thefirst and second conductive lines.
 80. The magnetic random access memoryaccording to claim 75, further comprising: a third conductive lineprovided in the second array, which is orthogonal to the firstconductive line.
 81. The magnetic random access memory according toclaim 76, wherein the first conductive line is isolated from the firstand second magneto resistive elements, and the third conductive line isconnected to the second magneto resistive element.
 82. The magneticrandom access memory according to claim 76, wherein the first and thirdconductive lines are connected to the second magneto resistive elementin parallel.
 83. The magnetic random access memory according to claim80, wherein the first, second and third conductive lines are writelines.
 84. The magnetic random access memory according to claim 68,wherein the first array unit has a third magneto resistive element andthe second array unit has a fourth magneto resistive element, whereinanother of the first conductive line is adjacent to the third and fourthmagneto resistive elements and is shared with the third and fourthmagneto resistive elements.
 85. The magnetic random access memoryaccording to claim 84, wherein the other of the first conductive line isconnected the third and fourth magneto resistive elements.
 86. Themagnetic random access memory according to claim 68, wherein the firstarray unit has a third magneto resistive element and the second arrayunit has a fourth magneto resistive element, further comprising: asecond conductive line as the write line, which extends in a directionin which the first and second array units are accumulated, and which isadjacent to the third and fourth magneto resistive elements, wherein thefirst and second conductive lines are connected each other at the topportion thereof.
 87. The magnetic random access memory according toclaim 68, further comprising: a selective transistor provided on thesemiconductor substrate and connected to one end of the first conductiveline.